Biobased Copolymers Composed of l‐Lactic Acid and Side‐Chain‐Substituted Lactic Acids: Synthesis, Properties, and Solid‐State Structure

Abstract

Various biobased copolyesters composed of L -lactic acid (LLA) and side-chain-substituted lactic acids (SLAs) with high molecular weight and LLA-rich composition are synthesized by direct solution polycondensation. Glycolic acid, 2-hydroxyisobutyric acid, ( S )-2-hydroxy-3-methylbutanoic acid (LVOH), and ( S )-2-hydroxy-4-methylpentanoic acid (LLOH) are chosen as SLAs. Wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) reveal that the substituent size of the SLAs determines whether or not SLA units are included in crystallites of the LLA sequences. Unlike poly( L -lactic acid), tensile necking is seen in the copolymers with 2 mol% LVOH and with 6 mol% LLOH. Enzymatic degradation is accelerated with increasing SLA content. Especially for 6 mol% LLOH, the SLA introduction improves both the mechanical properties and the enzymatic degradability.

Cocrystallization of monomer units in lactic acid-based biodegradable copolymers, poly(l-lactic acid-co-l-2-hydroxybutanoic acid)s

“…The crystalline lattices of copolymers should be similar with but different from those of homopolymers. Such shifts of 2q values depending on comonomer content are reported for other biodegradable polyesters which can cocrystallize [41,56,58]. In marked contrast with the precipitated and melt-crystallized samples, the solution-crystallized HB74, HB44, and HB27 copolymer samples were amorphous (Fig.…”

“…This indicates that the incorporated glycolide unit reduced the interplane distance (d) and strongly suggests the cocrystallization of Llactide and glycolide units in poly(L-lactide-co-glycolide) L-lactic acids (up to ca. 10 mol%) and found that glycolic acid, 2-hydroxy-2-methylpropanoic acid (i.e., 2-hydroxyisobutyric acid), and L-2-hydroxy-3-methybutanoic acid units with relatively small side chains are included in the crystallites of L-lactic acid unit segments, whereas L-2-hydroxy-4-methylpentanoic acid units with relatively bulky side chains are excluded from the crystallites [58]. However, as far as we are aware there has been no report on the cocrystallization of lactic acid or lactide unit with comonomer units in lactic acid or lactide-based copolymers for a wide comonomer unit content range including 50 mol%.…”

Effect of Chemical Composition Variant and Oxygen Plasma Treatments on the Wettability of PLGA Thin Films, Synthesized by Direct Copolycondensation

“…However, the melt transition of the PLA stereocomplexes of the homopolymers or the copolymers with glycolic acid mostly shifted towards a higher temperature range [28]. On the other hand, with the addition of the side chain-substituted PLA to the PLLA, a significant decrease in the melt transitions was observed [51]. In the presented results, any clear melt transition was not observed in any of the DSC thermograms of the PLGA copolymers, which shows that all of the copolymers are amorphous in nature.…”

Poly(styrene‐co‐maleic anhydride) ionomers as nucleating agent on the crystallization behavior of poly(ethylene terephthalate)

“…Furthermore, the degree of crystallinity ( ) for each sample is estimated from the following eq. (13): where the values of 2θ 1 and 2θ 2 used in this study are 10° and 40°, respectively. I c (2θ) is the diffraction intensity from the crystalline phase, and I a (2θ) is the diffraction intensity from the amorphous phases.…”